JP3422663B2 - Color tone control method and device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color tone control method and apparatus used in an offset printing machine or the like.

[0002]

2. Description of the Related Art When performing continuous printing, controlling the ink supply amount is most likely to affect image printing. This ink supply amount control is performed by visual evaluation of the colorimetric area printed with the image or by analysis of the colorimetric area with a color densitometer. An example of the latter is disclosed in German published patent application OS 2728738.

In practice, it is known that ink feed rate control based solely on measurements with a color densitometer is often inadequate. Therefore, when the same full tone density (solid density) is set, a considerable color difference (color difference) often occurs between the proof print or the temporary proof print and the final print. When such a color difference is detected, the color difference must be corrected by stopping the ink supply amount control and manually adjusting the ink supply amount. In addition, the cause of such a difference in the printed color is the difference in the generally different printing manufacturing methods of proof printing or temporary proof printing and final printing (printing machine of proof printing or temporary proof printing This is due to a difference in color due to the difference in the materials used (difference in the color of the used ink) and the difference in the materials used.
Furthermore, when printing with constant ink density printing, especially when controlling the ink supply rate with a constant full-tone density, fluctuations in color tone values (color tones formed by halftone dots) are due to fluctuations in ink temperature or fountain solution supply rate. Dot gain (thickness of halftone dots)
Is not a guarantee that a stable print color tone can be obtained as a result of defective ink transfer due to the change of the ink and paper powder piling (deposition).

Therefore, it is necessary to improve the ink supply control in the printing press so as to obtain a highly accurate match between the proof or tentative proof and the actual print. As one of the improved examples of the ink supply amount control, for example, Japanese Patent Laid-Open No.
There is a method and an apparatus described in Japanese Patent Laid-Open No. 2-146633.
The invention described in this publication relates to a method for controlling inking (ink supply amount) in a printing machine, a printing apparatus suitable for implementing the control method, and a measuring apparatus for generating control data for such a printing apparatus. It is described that the purpose thereof is to maintain the final printing in a stable state with respect to the ink supply, and further to make it possible to discern the color variation.

The summary of the above publication will be described below. FIG. 7 shows the configuration of the device disclosed in Japanese Patent Laid-Open No. 62-146633. The mutual relation of each device will be briefly described as follows. (1) Print sheet 4 printed by the printing machine 300
00 is measured by a photoelectric means (not shown). That is, a series of colorimetric areas in the print sheet 400, such as a generally preselected location in the printed image, or portions of the colorimetric area 410 that are printed simultaneously, are measured by photoelectric means. (2) The control data 110 corresponding to the color difference of the printing ink used for printing the individual print zones is the measurement value acquisition device 10 based on the measurement values obtained in (1) above.
Determined at 0. (3) The control data 110 is sent to the control panel 200 as an input value. (4) The control panel 200 uses the control data 110 so as to minimize the color difference.
A control data adjustment signal 210 for adjusting the ink control elements of the.

Next, a method for achieving the above object will be described as follows. (1) Convert the measured value (spectral reflectance of each colorimetric area) into color coordinates. A raster color tone (color tone by halftone dots of each color) is mainly used as the colorimetric piece to be measured, and it is also possible to select a colorimetric piece that fits a color tone particularly important for an image. (2) The preset color coordinate (target color coordinate) value is compared with the color coordinate (reference color coordinate) value of the measured value. (3) The ink supply amount is controlled so as to minimize the color difference vector (deviation between the target color coordinate value and the reference color coordinate value) generated in (2) above. That is, the color difference vector is multiplied by an empirically determined conversion matrix, and as a result, the color density difference vector is obtained. The color density difference vector component is
It consists of the density difference of each printing color or the ink film thickness difference. Therefore, if the color density difference vector (control data) is obtained, it acts to change the setting of the ink control element, and the color difference is minimized. (4) When a print sheet (OK sheet) determined to be satisfactory by the above method is obtained, in the final printing, the control method (ink supply amount control that minimizes the color difference) is stopped, and the printed matter of each color is stopped. Switching to ink supply amount control by a method for maintaining a constant color density (a method disclosed in German Patent Publication Gazette OS2728738). However, the color density is converted into a filter color density corresponding to the densitometer and used as the measured density without separately providing a measuring device. (5) If the color difference deviates from the allowable density range for some reason during the printing operation after switching to the density control, the control method is switched to the color difference control. (6) When the allowable color difference is reached, the set color density value is updated, and the density control is performed again.

[0007]

[Problems to be Solved by the Invention]

(A) Various color coordinates (L * a * b *, L * u * v *, etc.) values of the CIE International Commission on Illumination obtained from a certain spectral reflectance value are mapped to one point, but the same color There are countless spectral reflectance values as coordinate values. Therefore, in the control method based on the color coordinate matching according to the conventional technique, the color of the color sample (proof printing or temporary proof printing) and the final printing sheet match only on the color coordinates defined by a certain standard light source or visual field, If the type or field of view changes, a color difference occurs and the colors do not look the same.

The present invention has been made in view of the above problems, and an object thereof is to provide a color difference between a color sample (proof printing or temporary proof printing) and a final printing sheet even if the type of light source changes. It is to provide a color tone control method and apparatus that prevent the occurrence of the above problem.

[0009]

In order to achieve the above-mentioned object, in the method (apparatus) according to the present invention, a visible light region is provided for each of a plurality of color chips on a printing sheet printed by a multicolor printing machine. In the color tone control method (apparatus) in which the control data is calculated based on the measured spectral reflectance, the control data is calculated based on the measured spectral reflectance and the predetermined target spectral reflectance, and the control data is controlled by the control data. The measured spectral reflectance and the target spectral reflectance are compared for each color chart piece, the ink amount increase / decrease signal is calculated so that the deviation becomes the minimum value, and based on the ink amount increase / decrease signal obtained from the calculation result. In order to control the ink supply device, (a) a spectrum in the visible light region for each of a plurality of color chips (overlaid halftone color chips of cyan, magenta, and yellow) on a printing sheet printed by a multicolor printer. Measure reflectance And (b) a step (means) of calculating a spectral reflectance deviation between a measured spectral reflectance and a predetermined target spectral reflectance for each color chart piece, and (c)
A step (means) of filtering the spectral reflectance deviation with a color matching function and a spectral distribution of the observation light source;
A step (means) of integrating the filtered calculated value, and (e) an ink solid density such that the deviation between the measured spectral reflectance and the target spectral reflectance becomes a minimum value from the integrated value calculated by the integral. A step (means) for calculating the deviation and a step (f) for calculating an ink amount control signal from the ink solid density deviation are respectively provided.

Further, in the present invention, the integrated values ΔRx, Δ
Ry and ΔRz are calculated by the following equation (1).

[Equation 3]

In the present invention, the solid density deviation ΔDc of cyan ink, the solid density deviation ΔDm of magenta ink,
The solid density deviation ΔDy of the yellow ink is calculated by the following equation (2).
I am trying to calculate by.

[Equation 4]

As the color patch, a halftone color patch in which cyan, magenta and yellow are superposed is used.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a diagram schematically showing the configuration of a color tone control device (ink supply control device) 1 of a printing press that implements the color tone control method according to the present invention, and FIG. 2 implements the color tone control method according to the present invention. It is a figure which shows the flow at the time. As shown in FIG. 1, the color tone control device 1 of this example is
An ink supply device 2 for supplying ink to a multicolor printing machine, and a plurality of color chart pieces 5 (a cyan color as shown in FIG. 3) in a color tone inspection region 4 on a printing sheet 3 printed by this multicolor printing machine. Spectral reflectance measuring device 6 for measuring the spectral reflectance in the visible light region for each of magenta and yellow overlapping halftone color chips, and a target value input device for preliminarily inputting the data of the spectral reflectance of the target color. 7 and the above-mentioned spectral reflectance measuring device 6
And a display device 9 for displaying the calculation result of the calculation device 8 and a calculation device 8 to which the output from the target value input device 7 is supplied as a calculation element.
The calculation output from is supplied to the ink supply device 2 as an ink increase / decrease signal (control signal) 21.

Further, the above-mentioned arithmetic device 8 is a spectral reflectance deviation arithmetic unit to which the measured spectral reflectance output from the spectral reflectance measuring device 6 and the target value output from the target value input device 7 are respectively input. 10, a filtering calculation unit 11 to which the calculation output from the spectral reflectance deviation calculation unit 10 is supplied, an integration calculation unit 12 that performs integral calculation of a calculation value as a calculation result in the filtering calculation unit 11,
The solid density deviation calculation unit 13 to which the integrated value output from the integration calculation unit 12 is supplied, and the solid density deviation calculation unit 1
Ink amount control signal calculation unit 1 for supplying an ink increase / decrease signal 21 according to the calculation result in 3 to the ink supply device 2.
4 and.

Thus, in this example, <a> spectral reflectance deviation ΔR (λ) is obtained, and <b> spectral reflectance deviation ΔR.
(Λ) is subjected to a filtering operation, <c> the filtering operation value is integrated, and <d> the ink solid density ΔD is calculated from the integrated value, and <e> the ink solid density deviation ΔD. And the ink increase / decrease signal are obtained in advance to control the ink supply amount. Before explaining specific functions and operations of the apparatus of this example, the operation principle described in the above items <a> to <e> will be described item by item as follows.

<a> Spectral reflectance deviation ΔR between the measured spectral reflectance R (λ) and a predetermined target spectral reflectance Ro (λ)
(Λ) is calculated by the following equation (3).

[Equation 5]         ΔR (λ) = Ro (λ) −R (λ) (3)

<B> Next, as shown in the following equation (4), the spectral reflectance deviation ΔR (λ) is filtered by a color matching function and an observation light source (filtering spectral reflectance deviation ΔR '(λ). ))).

[Equation 6]

<C> Next, the calculated values ΔR'x (λ), ΔR'y (λ), and ΔR'z that have been filtered.
(Λ) is integrated as shown in the following equation (5).

[Equation 7]

<D> Next, from the integrated values ΔRx, ΔRy, and ΔRz obtained by the integral calculation, the measured spectral reflectance R (λ) is obtained.
The solid density deviation ΔD of the ink that minimizes the deviation ΔR (λ) between the target spectral reflectance Ro (λ) and the target spectral reflectance Ro (λ) is calculated by the following equation (2). That is, ΔRx, ΔRy, ΔR
ΔDc, Dm and Dy are obtained from z.

[Equation 8]

The coefficients a11 to a33 of the conversion matrix in the above equation (2) are obtained in advance. An example of a method for obtaining these coefficients a11 to a33 is as shown in Tables 1 and 2 below.

[Table 1]

[Table 2]

<E> Next, the ink supply amount is controlled by obtaining the relationship between the solid density deviation ΔD (ΔDc, Dm, Dy) of each ink and the ink increase / decrease signal in advance.

The reason why the filtering operation is performed as described above is as follows. That is, as will be described later, three colors (cyan, magenta,
In order to control the (yellow) ink, three pieces of information (the above integrated values ΔRx, ΔRy, and ΔRz) are calculated from the spectral reflectance.
Therefore, the spectral reflectance is filtered using a color matching function.

In the present embodiment, the number of print colors for which ink supply is controlled is not limited, but in the detailed description below, ink supply control for printing with commonly used printing colors cyan, magenta and yellow is used. The method will be mainly described based on the apparatus configuration diagram of FIG. 1 and the flowchart of FIG.

(I) FIG. 3 printed by a multicolor printer
The spectral reflectance in the visible light region is measured by the spectral reflectance measuring device 6 for each of the plurality of color charts 5 in the color tone inspection region 4 on the printing sheet 3 as shown in FIG. 2 (step S ₁ in FIG. 2). The above-mentioned spectral reflectance is the spectral reflectance of halftone halftone of cyan, magenta, and yellow, and solid color chips are not used in this example. Therefore, the solid density deviations ΔDc, ΔDm, ΔDy and the integrated values ΔRx, ΔR
The relationship between y and ΔRz is obtained in advance.

(II) Data of the spectral reflectance of a target color such as an OK sheet, a proof print, or a temporary proof print is input to the target value input device 7 in advance.

(III) Spectral reflectance deviation ΔR (λ) between the measured spectral reflectance R (λ) and the target spectral reflectance Ro (λ) is calculated by the spectral reflectance deviation calculator 10 in the arithmetic unit 8 ( Step S 2 in FIG. ₂ ). The calculation method is <a> above.
The equation (3) described above is used.

(IV) The spectral reflectance deviation ΔR (λ) is calculated with the color matching function and the spectral distribution S (λ) of the observation light source by the filtering operation unit 11 in the operation device 8 (step S in FIG. 2). ₃ ). As the calculation method, the above equation (4) described in the above section <b> is used. In this embodiment, the filtering operation is performed with the color matching function as shown in FIG. 4 and the spectral distribution S (λ) of the observation light source as shown in FIG. The observation light source includes an A light source or a C light source in addition to the D65 light source of this embodiment.

(V) Calculated values ΔR'x (λ), ΔR'y (λ), and ΔR'z (λ) that have been filtered are calculated by the integral calculator 12 in the calculator 8 (in FIG. 2). Step S ₄ ). The calculation method uses the above equation (5) described in the above item <c>. (VI) Integral values ΔRx, ΔRy, ΔRz calculated by integration
From the measured spectral reflectance R (λ) and the target spectral reflectance Ro
The solid density deviation ΔD (control data) of the ink such that the deviation ΔR (λ) from (λ) becomes the minimum value is calculated by the solid density deviation calculator 13 in the calculator 8 (step S ₅ in FIG. 2). ). The calculation method uses the equation (2) described above in the section <d>. The coefficient a of the transformation matrix
11 to a33 are solid density deviation ΔD of the ink of the sample printed in advance and the integrated values ΔRx, ΔRy, ΔR.
By examining z, it can be obtained by multiple regression analysis.

(VII) The relationship between the solid density deviation ΔD (control data) of the ink and the ink key opening 20 as shown in FIG. 6 is obtained, and the ink supply device 2 is used by using the relationship.
The ink key opening 20 of is calculated (step S ₆ in FIG. 2). In FIG. 6, 30 is an ink key, 31 is an ink source roller, 32 is an ink feeding roller,
33 is an ink roller group, where Q = M × h in the figure, Q is the ink supply amount, M is the ink source roller rotation amount, h
Is the ink key opening amount.

(VIII) The ink key opening 207 calculated in the above (VII) is sent to the ink supply device 2 as the ink increase / decrease signal 21, and the ink key opening corresponding to each printing zone 22 (see FIG. 3) is performed. Control 20 degrees.

[0031]

According to the control method by color coordinate matching according to the prior art, the color of the color sample (proof printing or temporary proof printing) and the color of the final printing sheet match only on the color coordinates defined by a certain standard light source or visual field. , If the type of observation light source changes,
Color difference occurs (does not look the same). On the other hand, in the method according to the present invention, by inputting the spectral distribution of the observation light source to the arithmetic unit, a color difference between the color sample (proof printing or temporary proof printing) and the final printing sheet occurs even if the type of light source changes. Can be prevented.

[Brief description of drawings]

FIG. 1 is a schematic block diagram showing an embodiment of an ink supply control device for a printing press according to the present invention.

FIG. 2 is a flow chart showing a flow when the ink supply control method according to the present invention is carried out using the apparatus of FIG.

FIG. 3 is a layout view of a color patch used in an embodiment of the present invention.

FIG. 4 is a characteristic diagram of a color matching function used in an embodiment of the present invention.

FIG. 5 is a characteristic diagram of a spectral distribution of an observation light source used in one embodiment of the present invention.

FIG. 6 is a diagram showing an ink supply mechanism when applied to a sheet-fed printing press which is an embodiment of the present invention.

FIG. 7 is a schematic block diagram embodying the prior art.

[Explanation of symbols]

1 Ink supply control device 2 Ink supply device 3 printed sheets 4 Color tone inspection area 5 color chips 6 Spectral reflectance measurement device 7 Target value input device 8 arithmetic unit 9 Display device 10 Spectral reflectance deviation calculator 11 Filtering operation unit 12 Integral calculator 13 Solid density deviation calculator 14 Ink amount control signal calculator 20 Ink key opening 21 Ink increase / decrease signal 22 Print band

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-62-146633 (JP, A) JP-A-8-132595 (JP, A) JP-A-3-56832 (JP, A) JP-A-6- 270395 (JP, A) JP-A-4-250041 (JP, A) JP-A-1-225554 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) B41F 31/02 G01J 3 / 46

Claims (6)

(57) [Claims] 1. A spectral reflectance in the visible light region is measured for each of a plurality of color chips on a printing sheet printed by a multicolor printing machine, and the measured spectral reflectance and a predetermined target spectral reflectance are measured. In the color tone control method in which the control data is calculated based on the control data and the ink supply amount is controlled by the control data, the measured spectral reflectance is compared with the target spectral reflectance for each color chart piece, and the deviation is the minimum value. In order to control the ink supply device based on the ink amount increase / decrease signal obtained from the calculation result of the ink amount increase / decrease signal so that (a) a plurality of printing sheets printed by a multicolor printing machine are printed. A step of measuring a spectral reflectance in the visible light region for each color chart piece, and (b) a step of calculating a spectral reflectance deviation between a measured spectral reflectance and a predetermined target spectral reflectance for each color chart piece, (C) Deviation of the spectral reflectance Filtering with a color matching function and the spectral distribution of the observation light source, (d) integrating the calculated values that have been filtered, and (e) measuring spectral reflectance from the integrated values that have been integrated. And a target spectral reflectance deviation having a minimum value, a step of calculating a solid ink density deviation, and (f) a step of calculating an ink amount control signal from the solid ink density deviation, respectively. Color control method. 2. The color tone control method according to claim 1, wherein the integrated values ΔRx, ΔRy, ΔRz are calculated by the following equation (1). [Equation 1] 3. The solid density deviation ΔDc of cyan ink, the solid density deviation ΔDm of magenta ink, and the solid density deviation ΔDy of yellow ink are calculated by the following equation (2). 2. The color tone control method described in 2. [Equation 2] 4. The color tone control method according to claim 1, wherein a halftone color patch in which cyan, magenta, and yellow are superposed is used as the color patch. 5. A spectral reflectance in the visible light region is measured for each of a plurality of color chips on a printing sheet printed by a multicolor printing machine, and the measured spectral reflectance and a predetermined target spectral reflectance are measured. In the color tone control device that calculates the control data based on the above, and controls the ink supply amount by this control data, (a) the visible light region of each of the plurality of color chips on the printing sheet printed by the multicolor printing machine Means for measuring the spectral reflectance, (b) means for calculating the spectral reflectance deviation between the measured spectral reflectance and the target spectral reflectance for each color patch, and (c) the spectral reflectance deviation for the color matching function and Means for performing a filtering operation with an observation light source; (d) means for performing an integral operation on the value obtained by the filtering operation; and (e) a minimum deviation between the measured spectral reflectance and the target spectral reflectance from the value obtained by the integral operation. The in Tone control apparatus comprising: means for calculating the solid density difference, characterized by comprising respective means, a to compute the ink amount control signal from the (f) the Inkibeta density deviation. 6. The color tone control device according to claim 5, wherein the color patch is a halftone color patch in which cyan, magenta, and yellow are overlapped.